Object sensing systems, also referred to as presence sensing systems, find utility in a variety of applications. In some areas of use, object sensing involves distance measurement. Distance measurement may be based on, for example, measuring the flight time of an emitted laser pulse based on sensing its return reflection from an object of interest. Applications ranging from surveying to hazardous machinery guarding may make use of such radiated signal distance measuring technology.
Measuring distance based on the flight time of an emitted laser pulse entails many challenges, with the task of maintaining an accurate time-of-flight measuring system standing foremost among those challenges. Because of the small intervals of time involved, precision and repeatability are paramount in producing accurate and reliable distance measurements. In some cases, the distance measurement application requires run-time verification of distance measurement accuracy, such as is required in safety-critical machine guarding applications. Maintaining guarding operations and object sensing performance in the face of these underlying run-time verification requirements exacerbates the challenges.
In many guarding operations, object sensing requirements relate to a given sector or field of view in advance of a hazardous area or point. Thus, object sensing necessarily extends over or across this field of view. One approach to effectively covering this field of view entails stepping a distance-sensing scanner across the field of view at sufficiently small steps to meet the required object detection resolution requirements. In some implementations, a laser scanner is configured to have a rotating scanning mechanism that repeatedly takes distance measurements at discrete angular points across a given field of view or sector. Return reflections from the angular scan points are evaluated to determine if the encroachment of any detected object violates configured guarding parameters.
One difficulty associated with installing, configuring, and monitoring presence sensing systems stems from the relative inscrutability of the system regarding its operation. That is, without some type of intelligent interface to the presence sensing system, it is difficult for an observer to glean much about the typical system""s operation, particularly regarding the relative position of detected objects within the system""s field of view.
Ideally, where the system is configured as a relatively wide field-of view system, it should include position indicators, such as azimuthally arranged visible indicators that may be used to indicate the relative angles or directions to one or more objects detected within the system""s field of view.
The present invention comprises a method and apparatus enabling a presence sensing system to visibly indicate where detected objects lie within its field of view. This visible indication greatly aids an observer in verifying, troubleshooting, and monitoring the system""s presence sensing operations.
Commonly, the system is configured to monitor a field of view in advance of a hazardous area, such as in machine guarding applications where the system monitors a physical area in advance of hazardous machinery. In this type of application, the system may be configured with an array of detection indicators, with individual ones of the indicators corresponding to particular portions of the system""s field of view. Thus, by illuminating the indicator most closely corresponding to the relative angle or position of a detected object, the system provides the observer with valuable information regarding the location of a detected object within the system""s field of view.
Use or activation of the detection indicators may vary depending upon the system""s operating mode. In some configurations, the indicators are active only in certain modes, such as a troubleshooting or installation modes. In other configurations, the detection indicators are active during the normal course of operation. Additional variations exist regarding the arrangement of indicators, and type of indicator used. For example, the indicators may comprise an array of discrete LEDs, or may comprise an integrated LED or LCD assembly. Other indicator types, such as neon or incandescent lamps may be desirable in some configurations. Further, the indicators may be single color or may employ two or more colors, where the illuminated color, for example, might be chosen based on the detected object""s distance.